JS: fix panic when 'for(let ' has bad syntax, see #108

js/parse.go

@@ -328,7 +328,9 @@ func (p *Parser) parseStmt(allowDeclaration bool) (stmt IStmt) {
 			tt := p.tt
 			p.next()
 			varDecl := p.parseVarDecl(tt, true)
-			if p.tt != SemicolonToken && (1 < len(varDecl.List) || varDecl.List[0].Default != nil) {
+			if p.err != nil {
+				return
+			} else if p.tt != SemicolonToken && (1 < len(varDecl.List) || varDecl.List[0].Default != nil) {
 				p.fail("for statement")
 				return
 			} else if p.tt == SemicolonToken && varDecl.List[0].Default == nil {

js/parse_test.go

@@ -453,6 +453,7 @@ func TestParseError(t *testing.T) {
 		{"for(a;a;a", "expected ) instead of EOF in for statement"},
 		{"for(var [a],b;", "unexpected ; in for statement"},
 		{"for(var [a]=5,{b};", "expected = instead of ; in var statement"},
+		{`for(let{[(`, `unexpected EOF in expression`},
 		{"for await", "expected ( instead of EOF in for statement"},
 		{"function a(){for await", "expected ( instead of await in for statement"},
 		{"async function a(){ for await(a;", "expected of instead of ; in for statement"},